The present invention relates to the field of producing ophthalmic and/or optical lenses which can be designed, for example, in the form of in particular plastics material-based spectacle glasses or plastic spectacle glasses, starting from corresponding lens blanks or spectacle glass blanks.
For the purposes of subsequent machine processing—in particular in the form of grinding, machining and/or polishing operations—to obtain the finished lenses or spectacle glasses, blanks of this type are generally firstly fixed with the help of a blocking agent composition to a carrier or block (block piece), and/or stuck to this, in order, in so doing, to ensure as rigid and secure as possible a fixing of the blank during the processing operations, which can considerably increase the quality of the finished product.
In particular, the present invention relates to an (adhesive) composition, in particular a blocking agent composition or a blocking agent with which the ophthalmic or optical lenses or plastics material-based blanks to be processed can be fixed to a carrier or block for the purposes of further processing.
Moreover, the present invention relates to a method for fixing the aforementioned blanks to a carrier structure such as a block or block piece, using the (adhesive) composition according to the invention.
Furthermore, the present invention relates to a composite which has a carrier or block or a block piece and also a blank of the aforementioned type fixed to the carrier, where the blank is fixed to the carrier by means of the composition according to the invention.
Furthermore, the present invention relates to a process for producing an ophthalmic or optical lens, preferably a plastics material-based spectacle glass, where a further processing of the blank fixed to a block by means of the composition according to the invention takes place in order to obtain, in this way, the finished product in the form of an ophthalmic or optical lens, preferably a plastics material-based spectacle glass. The resulting product here can optionally also be subjected to further (post-) processing steps, such as a coating treatment or a coating.
Moreover, the present invention relates to an ophthalmic or optical lens, thus those which are obtainable by the method according to the invention.
Furthermore, the present invention relates to the use of the composition in producing ophthalmic and/or optical lenses, preferably plastics material-based spectacle glasses.
Finally, the present invention relates to the use of the composition, in particular blocking agent composition, according to the invention for fixing a spectacle glass blank to a carrier, in particular a block piece.
In the course of the production of in particular plastics material-based spectacle glass blanks or ophthalmic and/or optical lenses, in the prior art, the procedure has generally involved fixing a corresponding blank based on plastic material, which is often present in poured form with an optical quality, to a carrier structure or a block in order to allow machine processing of the side of the blank facing the block and/or a shaping of the blank per se. The blank can generally be spherical in shape, where the particular sides of the blank can have radii formed independently of one another. Equally, however, the blank can also have at least one flat side. The blank can be fixed to the carrier structure or the block with one of its spherically shaped sides and, in the case of the presence of a flat side, preferably with the flat side. In this way, on the one hand, the optical properties of the blank can be modified and, on the other hand, a shaping of the spectacle glass, for example with regard to a tailoring to a spectacle frame, can be made possible. In this connection, methods known per se for example to the person skilled in the art on the basis of machining, milling, turning, grinding, polishing or the like are used.
The carrier or block provided for accommodating the blank functions here equally as coupling part for accommodation in a corresponding processing machine, where the coupling section of the block in this regard is generally arranged and/or configured on the side of the carrier facing the blank to be fixed. In the course of the fixing or attachment of the blank to the carrier or block, the procedure generally is such that, between block on the one hand and blank on the other hand, a cavity is established which is filled or refilled with an adhesive or a blocking agent composition in order, in this way, to make possible a fixing of the blank. After the machine processing of the blank has taken place, the blank or the resulting spectacle glass or the resulting optical lens is detached from the composite, which can take place for example using mechanical and/or thermal methods.
For the purposes of fixing or for refilling the cavity, the spectacle glass blank to be blocked is generally arranged above the block or laterally to the block inclined or tilted in this case, where, in both cases, the blank is arranged spaced apart from the face or receiving surface of the block. To provide a cavity to be filled by the adhesive mass or blocking agent composition, a sealing means, in particular a blocking ring, can be used for the sealing limitation and thus to a certain extent as sealing or sealing device (sealing ring) and also optionally a guide cap between the spectacle glass blank on the one hand and the block piece on the other hand. The formation or sealing of the cavity can optionally be flanked by a so-called guide cap and/or by a receiving cap, which in general can be arranged below the blank and can be assigned functionally to a blocking machine used in the course of the blocking. In general, the volume of the cavity is about 25 to 40 cm3, where the cavity is filled with a corresponding amount of adhesive or blocking agent composition. In general, to accommodate the carrier, the block has a diameter of about 43 mm, in which case it is usually provided that the blank, which generally has a diameter of about 60 to 85 mm, is fixed in particular in a concentric manner to the block such that the blank juts out over the block along the entire periphery of the block. The blank can likewise also be fixed to the block in the form of a prismatic tilting and/or in a decentered manner.
In general, the procedure can be such that, for blocking a spectacle glass blank on a block or block piece, both the block piece and also the spectacle glass blank are placed in a blocking device or machine. The blocking machine can have a receiving cap for receiving the block piece. For the purposes of lining up the block piece or the receiving cap relative to the spectacle glass blank, moreover, a guide cap can be provided, which can be stored e.g. above a swivel plate in the blocking machine. The spectacle glass blank to be blocked can be positioned above the block piece where, for the purposes of forming a cavity to be filled with the block composition, a blocking ring, configured as sealing limit or sealing means, and/or a guide cap can be arranged between the spectacle glass blank and the block piece or the receiving cap. In this connection, the blocking ring can provide a seal, for the sealing formation of the cavity against the spectacle glass blank and also against the guide cap and/or the block piece. The guide cap can provide a seal against the receiving cap and/or the block piece. The block composition can be introduced into the cavity via a filling opening attached in particular in the blocking ring.
A device for blocking a spectacle glass blank on a block or a block piece by means of a bonding mass is described e.g. in DE 30 35 989 A1. Using the device described therein, a low-melting metal alloy can be used as bonding mass which, on account of gravitational force, is filled from a storage container into the cavity by means of a filling point.
DE 103 04 388 A1 relates to a block piece for accommodating a blank which is designed to be machinable. In this connection, however, the blank is not fixed to the carrier using a thermoplastic adhesive mass. Instead, an adhesive film is used for the fixing where, in this connection, from time to time, a holding part, preformed specifically with regard to the blank, has to be used in order to permit fixing of the blank over the largest possible area.
Furthermore, DE 10 2005 038 063 A1 relates to a preformed block piece with three receiving points for accommodating a lens blank where, as a result of a specific configuration of the block piece, the amount of adhesive agent to be used is intended to be reduced to a minimum.
EP 0 851 800 B1 also relates to a block for lens blanks in which the lens blank, however, is fixed by means of a mass, that has become solid, of a thermoplastic holding mass based on a homopolymer or copolymer of ε-caprolactone.
In the prior art, numerous approaches are known for the fixing or adhesion of blanks for ophthalmic or optical lenses or for spectacle glasses on carrier structures for the purposes of subsequent machine processing, where a primary objective can be considered that of permitting a secure and durable connection between lens or spectacle glass blank on the one hand and carrier or block piece on the other hand, so that the unit resulting in this way with the blank can withstand the forces which arise during the subsequent machine processing.
In this connection, in the prior art, metal alloys are often used as adhesive mass which, in general, have a low melting temperature in the region of about 50° C., in order to permit on the, in particular semi-finished, surface of a blank a bonding or fixing with a block facing the blank such that, in this way, the side of the spectacle glass blank facing the block is accessible to subsequent processing. An attachment of this type is generally also referred to in the prior art as “lens blocking”.
A metal alloy, known in the prior art, with low melting temperature can include e.g. the elements bismuth, tin, lead, cadmium, indium and antimony. An alloy of this type has a lower melting point than the individual elements, which is sometimes of importance during the fixing of plastics material-based blanks for avoiding temperature-induced damage.
The disadvantage of alloys of this type in the prior art is the fact that they pose a considerable environmental and/or health risk, particularly since numerous ingredients of the alloy are severely toxic and sometimes are also regarded as so-called protoplasma toxins which, upon entry into the human body, for example as a result of inhalation or skin absorption, can lead to health impairment. These risks are of importance particularly against the background that, in the course of the processing of spectacle glass blanks, on account of the processing methods used, dust particles, fine dust particles or smoke particles can be released, which can lead to a considerable exposure of the environment to the harmful substances. Furthermore, with regard to the metal alloys known in the prior art, it is disadvantageous that these are firstly expensive, especially since they cannot be recycled per se, and that, secondly, also an only limited use spectrum is possible to the effect that, especially on account of the high material costs, only certain blanks with specific geometries can be fixed.
As alternatives to the metal alloys described above, it has also been attempted in the prior art to replace these by plastics material compositions, which include, for example, thermoplastic resins. However, compositions of this type generally do not always have optimum physical properties. In particular, compositions of this type are relatively brittle, and also the cohesive force and tensile strength are not always optimal. Moreover, compositions of this type, especially during the processing of the blank, can become deformed or become too soft, which has an adverse effect on the quality of the spectacle glass to be produced since the surface can become irregularly shaped. Moreover, the cleaning of the spectacle glasses or lenses from these compositions is difficult and sometimes very time-intensive, which further increases the costs of the production of spectacle glasses overall.
EP 0 968 074 B1 relates to a thermoplastic lens receiving material based on plastics material, the focus being in particular on the use of homopolymers or copolymers of ε-caprolactone for the composition described therein. The compositions described therein are disadvantageous in so far as the starting materials are relatively expensive and the compositions, moreover, do not have good thermostability. Also, the adhesive properties are sometimes not always adequate.